Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 1 - First-Order Differential Equations - 1.12 Chapter Review - Additional Problems - Page 111: 47

Answer

See below

Work Step by Step

Given: $$(x^5+y^m)dx-x^ny^3dy=0$$ a) For our equation: $M_y'=my^{m-1}\\ N'_x=-nx^{n-1}y^3$ The only solution that satisfies this condition is: $m=n=0$ b) Rewrite the given differential equation in the equivalent form: $\frac{dy}{dx}=\frac{x^5+y^m}{x^ny^3}$ then $m=0,n \in R$ c) To get a homogeneous equation from the given equation, we rewrite: $\frac{dy}{dx}=\frac{x^5}{x^ny^3}+\frac{x^m}{x^ny^3}$ Thus, the solution to this is: $m=5\\n=2$ d) This is a Bernoulli equation where $\frac{dy}{dx}-x^{-n}y^{m-3}=x^{5-n}y^{-3}$ Divide both sides by $y^{-3}$ we have: $\frac{1}{y^3}\frac{dy}{dx}-x^{-n}y^{m}=x^{5-n}$ There is no value for $m$ or $n$ for which our equation is linear. e) From (d), we get: $\frac{dy}{dx}-x^{-n}y^{m-3}=x^{5-n}y^{-3}$ The value that satisfies the condition for the Benourlli equation is: $m=4$ and $n$ can be arbitrary number.
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